Electromagnetic control device



Dec. 2, 1952 J HAGEN 2,620,466

ELECTROMAGNETIC CONTROL DEVICE Filed ma 31, 1950 v Summer /5. JERRYHAGEN Gnomeg Patented Dec. 2, 1952 UNITED ELECTROMAGNETIC CONTROL DEVICEApplication May 31, 1950, Serial No. 165,345

'7 Claims. (Cl. 323-94) My invention relates to electromagnetic type ofcontrol devices and particularly to devices of this general type havingelectrical signal outputs and employing magnetic fluids as a portion ofa magnetic circuit.

The use of magnetic fluids in control devices is a relatively recentadvancement in science which has heretofore been applied primarily tothe field of clutches and similar devices wherein the magneticproperties of the magnetic fluid alone have been utilized. In thepresent invention not only the magnetic properties of the fluid areutilized but also its property of electrical conductivity. This newmagnetic device comprises a magnetic core structure having a pluralityof air gaps therein Within one of which is located a quantity ofmagnetic fluid. The fluid therein is connected in a series relationshipwith a load circuit supplied by a signal for energizing the same. Acontrol or energizing winding on the core structure selectively andvariably magnetizes the core structure and the fluid in the gap makingit conductive to amplify, modulate, or otherwise modify the signalsupplied to the load circuit.

It is therefore an object of this invention to provide a new and novelelectromagnetic control device utilizing the variable resistanceproperties of a magnetic fluid for varying an electrical signal outputof the device.

It is also an object of this invention to provide a device of themagnetic fluid type which is capable of modulating, amplifying orotherwise modifying electrical signals.

Another object of this invention is to provide in a device of this typea means for retaining the magnetic fluid in an air gap of a magneticcore structure.

A further object of this invention is to provide a device of this typewith an improved means for holding the magnetic fluid distributed in theair gap of the magnetic core structure of the device.

till another object of this invention is to provide in a device of thistype means for substantially eliminating residual magnetism in the corestructure and its effect upon the magnetic fluid in the air gap.

It is further an object of this invention to provide in a device of thistype a means for inserting a bias or saturating flux in the corestructure of the evice to increase its sensitivity.

Theseand other objects of this invention will become apparent'from areading of the attached description together with the drawings wherein:

Figure 1 is a schematic disclosure of the magnetic control device of thesubject invention shown as a modulator for a D. C. signal in a loadcircuit connected to the device,

Figure 1A shows in section another arrangement of a container to bepositioned in the air gap of the core structure of the device shown inFigure 1 the container positioning a magnetic fluid in the respectiveair gap of the core structure of the device,

Figures 2, 3 and 4 are schematic disclosures of the same magneticcontrol device utilizing difierent arrangements of controlling and loadsignals connected to the device, and

Figure 5 is another modification of the magnetic control device whichdiscloses the use of a biasing magnet in the magnetic circuit of thedevice.

My invention, which is shown schematically in the drawings, comprises amagnetic core structure Ii] having a plurality of air gaps H, [2therein. For simplicity, the core structure is shown as a pair ofU-shaped core members [3 and M of magnetic material positioned withtheir bifurcated extremities in near abutting relationship to define thegaps ll, [2 therebetween. A frame 20 of nonmagnetic and nonelectricallyconductive material holds the core members I3, [4 in assembled andspaced relationship. It is to be understood that this structure isintended to be illustrative only and that the shape and arrangement ofthe core members l3, l4 and the frame 28 together with the location ofthe gaps II and [2 may be varied within the scope of the teaching andoperation of this device as will become apparent as this disclosureproceeds.

The core members l3, M at air gap H may be separated by a block ofelectrical insulating material, the block being indicated at 2!, whichblock will aid in the spacing of the core members and will also prohibitan electric circuit between the members at this point. However, the airgap H alone may be employed as an electrical insulator when the coremembers It, It are spaced apart by means of the frame 23.

Within gap i2 formed by core members it, it of core structure it ispositioned a quantity of a magnetic fluid indicated at 23, the magneticfluid being composed of a plurality of magnetic particles suspended in aliquid having an oil base. The fluid 23 may be positioned or held in gapl2 by any suitable means but the magnetic or iron particles Within thegap E2 must be the only electrical conductor across the gap between thecore members I3, hi. I have found that containers such as is shown at 25and 26 in Figure l and 1A respectively are highly advantageous forhousing the magnetic fluid and spacingthe core members 23, Id.

Container 25 which is shown in Figure 1 is formed of a plastic orinsulating tube 2! into the ends of which copper or iron or otherelectrical or magnetic material end plates 28 are threaded. Tube 27 hasa shoulder or ridge portion 32] on its inner surface which spaces theend plate 28 with respect to the tube 2 The magnetic fluid 23 is addedto the container 25 before assembly of the plates 28 on the tube 21 iscompleted. The container is so positioned between the extremities ofcore members 13, I 3 forming the gap [2 that the end plates abut thecore members and are in magnetic and electrical contact therewith. Wheniron is used as the material in the end plates 28, these end plates actas a mere continuation of the core members which abut the container 25.Copper or other electrical or nonmagnetic materials are used in the endplates 28 to cut down the eiiect of residual magnetism in the corestructure H3 in a Well known manner.

Container 25 which is shown in Figure 1A is similar to the container 25disclosed in Figure 1 and either may be substituted in the corestructure IE shown in Figure 1 or in any of the core structures in thefigures later to be described. The container 25 difi'ers from container25 in that a plurality of layers of cloth 3| or other woven or fibrousnonmagnetic and nonelectrically conductive material is placed in thespacing or opening within the container and in contact with the magneticfluid 23. This cloth or fabric acts as a wick and tends to distributethe magnetic fluid uniformly within the opening of the container 2% andbetween the end plates 28 thereof. Such an arrangement tends to guardagainst settling of the magnetic particles within the fluid which underideal circumstances remains in suspension in the oil base at all times.

As noted above, the magnetic fluid 23 in gap 12 is also util zed as anelectrical conductor connecting the core members 13, i l forming the gapin an electrical circuit 69 to be described below. Connected to the coremembers l3, Hl adjacent the air gap l2 are a pair of conductors 4i and42 which lead to the electrical circuit 43 and which is adapted to beconnected to an external load, this circuit also being adapted to beenergized by a signal source of variable magnitude and phase as willbecome evident as this disclosure proceeds. In Figure 1, the load orelectrical circuit 49 includes the magnetic fluid 23 in gap l2,conductor 6!, a wiper M of a potential divider apparatus the winding dof which is connected in a series relationship with a D. C. batterysource it. This electrical load circuit is completed from winding d5through a load resistor A! and conductor 32 to the fluid 23 in gap I2. Apair of output terminals 58 are connected across the load resistor i? tosupply the external load (not shown) with the voltage drop across theresistor ll. Depending upon the type of load employed, the load resistorll may or may not be included in the load circuit d0. Variations in thesignal impressed on load circuit 43 may be had by Varying the positionof wiper M on Winding &5.

It is also to be understood that where the core structure H3 is suppliedWith only one air gap then the conductors to the electrical circuit areto be placed directly in contact with the magnetic fluid, such as beinglocated within the con- 4 tainer holding the same and electricallyinsulated from the core structure. In this manner the electric circuitcan be only completed through the magnetic fluid.

The core structure ill also includes a con trolling winding 52 whichwinding is positioned on the core structure to be common to both of themagnetic members 53, is such that when the winding is energized theportions of the members 13, M adjacent gap 12 will be energized withopposite magnetic polarities. In Figure 1, an A. C. energizing source isadapted to be connected to the winding 52 which acts as a controlling ormagnetizing winding for the core structure it. The alternating flux setup in core structure it] due to the energization of coil 52 from the A.C. source magnetizes the core members !3, I4 and hence the magneticfluid 23 in gap I? with alternating magnetic polarities thereby causingthe magnetic particles in the fluid to align and disalign with eachreversed or alternation of current flow providing simultaneously anelectrical conductor across the gap 12. As the particles in the fluidalign under the influence of the magnetic field the resistance of theconductor formed thereby decreases permitting increased current flow inthe load circuit ii! connected in series therewith. In this manner achopped or pulsed or modulated direct cur rent signal will flow into theload circuit 69 and the voltage drop across the resistor M takes on amodulated wave form which will be impressed across the output terminals53.

In Figure 2 is shown another embodiment of the invention utilizing thesame core structure Ill as that employed in connection with Figure l anddiscussed above. For simplicity the details of the core structure it andthe frame 26 which positions the same are omitted in the discussion andinthe drawings but it is to be understood that they are to be includedwith this embodiment. In Figure 2 there is shown the core members I3, I4With the air gaps H and i2 formed therebetween, the controlling Winding52 mounted on the core structure It and the container 25 positioned inair gap I2 to house the magnetic fluid 23. This embodiment utilizes asomewhat difierent type of D. C. signal supply which is adapted to beconnected to the load circuit as and in series with the fluid 23 in gapl2. This D. C. signal source comprises a bridge type of supply whichincludes a tapped resistor 55 conadapted to be connected to an A. C.source but a half wave rectifier 69 is included in this energizationcircuit to modify the controlling current in a manner to be laterdescribed. 'The pulsed A. C. supplied to the energizing winding due tothe half wave rectifier 69 causes a pulsed unidirectional flux flow inthe magnetic core structure It] and variable unidirectional magneticpolarities across the gap I2. This pulsed magnetization similarlymagnetizes the particles in the magnetic fluid 23 to make and break theload circuit at the air gap E2. The output across the load resistor 41or at the terminals 59 will thereby be .a modulated D. C. .of the samefrequency as the frequency .of the AC. input to coil-52.

The disclosure of Figure .3 also employs the same magnetic corestruc'tureas that .shown in the device of Figure :1,.hence the detailsof that portion of the circuit will .be :ornittedhere. The load circuit10 connected in series with gap [2 and across the load terminals 50 issubstantially the same as the load circuit 40 employed in connectionwith Figure 2 except that the signal source is energized by analternating current source of power. Similarly the energizing orcontrolling winding 52-onthe core structure It) is adapted to beenergized bya selectivel variable D.-C. source of power. Theoutput ofthis'circuit is an amplification of the A. C. supply or signal impressedon the load circuit 4'8 depending upon the variation in magnitude'of.the energizing currentsupplied to winding:52.

In Figure 4 there is shown another embodiment of this device in whichthe core structure is similar to the embodiments described above. Forthis reason the details of the core structure are omitted here. acts asa mixer or modifier of alternating load signals. The load resistor 4'1and magnetic fluid 23 are connected in series with an alternatingcurrent source of power omitting any bridge arrangement. put circuitwhich includes the conductor 4! connected to the alternating source,core member 13, the magnetic fluid 23 in gap l2, core member l4,conductor 42, and load resistor 41 to a ground connection 6! for thereturn side of the A. C.

source. The output terminals or load terminals 50 are as beforeconnected across the load resistor 4! but the load resistor 41 may beomitted if desired. The alternating signal impressed on this loadcircuit 80 and across the resistor 4? will be modified by the frequencyof the A. C. supply energizing coil 52 mounted on core structure ill. Asis apparent from the drawing, the alternating magnetization of corestructure due to the magnetization of the magnetic particles of fluid 23makes or breaks the electrical conductor formed at the air gap 12permitting current to flow in the load circuit 89 only during periodswhen the load circuit is completed.

The disclosure of Figure is another embodiment substantially the same asthat disclosed in Figure 2 employing a bridge type D. C. signal loadcircuit 40 and a rectified controlling input to the winding 52 mountedon core structure ill. of Figure 2 in that it includes a U-shapedpermanent magnet 65 the extremities of which are positioned adjacent thecore members l3, l4 bridging the gap ii in which the magnetic fluid 23is located. A magnetic flux created by the permanent magnet 65 overcomesthe initial permeability of the magnetic circuit formed by corestructure It and magnetic fluid 23 tending to saturate this portion ofthe magnetic circuit and increase the sensitivity of the device. Thepulsating current flow in coil 52 is in such a direction as to beadditive with the permanent magnet flux in aligning the particles of themagnetic fluid. The permanent magnet also serves an additional purposein that its strength is chosen to keep the magnetic particles partiallyaligned in the air gap l2 thereby aiding in keeping the particlesdistributed in the air gap and in suspension in the fluid.

Magnet 65 further operates in the same man- This particular embodimentThis arrangement provides an out- This disclosure Varies from thedisclosure ner as rectifier 60 in'that its unidirectional flux aids andopposes the alternating flux from an unrectified .-A. C. input to coil52 such that .the load current willh'avethe same .frequencyas thecontrolling input signal. Therefore magnet may sometimes be used toreplacerectifler B0.

Numerous objects and advantages of myinvention have been set .forthabove .in the foregoing description together with details of structureand function of the inventioniand the novel features thereof are pointed.out in the appended claims. These disclosures, however, are intended tobe illustrative only and Imay make changes in details (especially inmatter of shape, size vandarrangement of parts) within the principle ofthe invention to the full extentindicated by the broad generalmeaning ofthe terms in which the appended claims are expressed.

I claimas my invention:

1. In a device of the class describeda magnetic core structure having apair of fixed air gaps therein, a container of electrically insulatingmaterial having electrically conductive end plates positioned in one ofsaid air gaps :with said end plates abutting said core structure aplurality of magnetic particles suspended in a fluid and positioned insaid-container, means included .in said container adapted to hold saidmagnetic particles in a dispersed relationship, electrical circuit meansadapted to be energized from an adjustable source of power and includingan output circuit, said electrical circuit means being connected inseries'with said one of said air gaps, andmeans for magnetizing saidmagnetic core structure such that portions of said structure on eitherside of said one ofsaid air gaps are polarized with magnetic polaritiesof varying magnitudes.

2. In a device of the class described, a magnetic core structure havinga pair of fixed air gaps therein, a container of electrically insulatinmaterial having electrically conductive end plates positioned in one ofsaid air gaps with said end plates abutting said core structure, aplurality of layers of nonmagnetic and nonelectrically conductivefibrous material positioned in said container, a plurality of magneticparticles suspended in a fluid and positioned in said container beingheld in a dispersed relationship by said fibrous means, electricalcircuit means adapted to be energized from an adjustable source of powerand including an output circuit, said electrical circuit means beingconnected in series with said one of said air gaps and means formagnetizing said magnetic core structure such that portions of saidstructure on either side of said one of said air gaps are polarized withmagnetic polarities of varying magnitudes.

3. In a device of the class described, a magnetic core structure havinga plurality of fixed air gaps therein, a plurality of magnetic particlessuspended in a fluid and positioned in one of said air gaps, electricalcircuit means connected in a series relationship with said one of saidair gaps and having output terminals adapted to be connected to anexternal load, means mounted on said core structure for magnetizing saidcore structure such that portions of said structure on either side ofsaid one of said air gaps are polarized with magnetic polarities ofvarying magnitudes, and a magnetic biasing means of predeterminedpolarity and magnitude positioned adjacent said portions of said corestructure forming said one of said air gaps.

4. In a device of the class described, a magnetic core structure havinga plurality of fixed air gaps therein, a plurality of magnetic particlessuspended in a fluid and positioned in one of said air gaps, electricalcircuit means connected in serie relationship with said one of said airgaps and having output terminals adapted to be connected to an externalload, means mounted on said core structure for magnetizing said corestructure such that portions of said structure on either side of saidone of said air gaps are polarized with magnetic polarities of varyingmagnitudes, and a U-shaped permanent magnet of fixed polarity andmagnitude positioned adjacent said portions of said core structureforming said one of said air gaps.

5. In a device of the class described, a magnetic core structure havinga plurality of fixed air gaps therein, a plurality of magnetic particlessuspended in a fluid and positioned in one of said air gaps, electricalcircuit means connected in a series relationship with said one of saidair gaps and having output terminals adapted to be connected to anexternal load, means mounted on said core structure for magnetizing saidcore structure such that portions abutting said portion of said corestructure ad- 5 jacent said one of said air gaps.

6. In a device of the class described, a magnetic core structure havingat least one air gap therein, a plurality of magnetic particlessuspended in a fluid positioned in said air gap, electrical circuitmeans including an output resistor adapted to be energized from anadjustable source of power, said circuit being connected to saidmagnetic particles in said air gap, means mounted on said core structureadapted to energize said core structure and thereby magnetize saidparticles in said air gap, and a magnetic biasing means of predeterminedpolarity and magnitude positioned adjacent to portions of said corestructure forming said air gap.

7. In a device of the class described, a magnetic core structure havinga pair of air gaps therein, a container of electrically insulatingmaterial having electrically conductive end plates positioned in one ofsaid air gaps with said end plates abutting said core structure, aplurality of magnetic particles suspended in a fluid and positioned insaid container, electric circuit means adapted to be energized from anadjustable source of power and including an output circuit, saidelectrical circuit means being connected in series with said one of saidair gaps, winding means mounted on said core structure adapted to beenergized by a rectified alternating current signal, and a U-shapedpermanent magnet of fixed plurality and magnitude positioned adjacentsaid portions of said core structure forming said one of said air gaps.

JERRY HAGEN.

REFERENCES CITEB The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 774,922 Troy Nov. 15, 19042,500,953 Libman Mar. 21, 1950

